25 Permanent Magnet Motor Design.pdf
January 31, 2017 | Author: bitconcepts | Category: N/A
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Permanent Magnet Synchronous Motor (PMSM) Design
Part 1 – General Considerations
Permanent Magnet (PM) Motor
Characterized by permanent magnets on rotor Known for its simplicity and low maintenance No copper loss on rotor High efficiency
Exploded View of a PM Motor
J. R. Hendershot and T. J. E. Miller, Design of Brushless Permanent Magnet Machines 2nd Edition, p. 44, Motor Design Books LLC, 2010.
Inner Rotor Possibilities (1)
surface radial magnet
surface parallel magnet
breadloaf magnet
ring magnet
Inner Rotor Possibilities (2)
(e) IPM in Toyota Prius
Toyota Prius Hybrid Electric Vehicle (HEV) 3
1. 2. 3. 4.
Four cylinder combustion engine; Generator/starter; Electric Motor; Power split device (PSD)
J. F. Gieras, Permanent Magnet Motor Technology Design and Applications, 3rd Edition, p. 282, CRC Press, 2010.
2 J. R. Hendershot and T. J. E. Miller, Design of Brushless Permanent Magnet Machines 2nd Edition, p. 34, Motor Design Books LLC, 2010.
Segmented Magnets in Large PM Rotor
J. R. Hendershot and T. J. E. Miller, Design of Brushless Permanent Magnet Machines 2nd Edition, p. 94 & 602, Motor Design Books LLC, 2010.
Rotor Skew
stepped magnet
Magnetization Profile parallel magnetization
radial magnetization
most popular
radial sine magnetization
sine angle or sine direction magnetization
Halbach Array (1)
R. Krishnan, Permanent Magnet Synchronous and Brushless DC Motor Drives, p. 25-30, CRC press, 2010.
Halbach Array (2)
FEA
Halbach Array (3) Airgap Flux Density
Rotor is outside
Stator Volume and Size 2
Dl V0 T
T
Pout
m
Typically
V0 8 ~ 9 in / (ft lb) for 10hp or less (air cooled) 3
V0 4 ~ 5 in / (ft lb) for 10hp or more (water cooled) 3
The unit for D and L is inch. If we design D=L, we have the stator bore (inner) diameter estimated
Destimated (TV0 )
1 3
We can pick up D close to Destimated.
Stator Core Design core gap , per half pole pitch leff
/P
0
Bg ( a )ris d a
2 /2 D leff Bg , pk cos( ae )d ae 2 P 0 D leff Bg , pk P
Bcore , pk
core DB g , pk leff d c k i li Pd c k i li
tooth l eff
B tooth
0
(1)
B g ( ae ) ri d ae B g , pk s l eff
s B g , pk l eff tooth t s k i li t s k i li
(2)
Take t s 0.5 s , Bcore , pk 0.8 Btooth dc
D 1 .6 P
Effect of Pole Number on Yoke Flux Density Finite Element Analysis
with the same dc J. R. Hendershot and T. J. E. Miller, Design of Brushless Permanent Magnet Machines 2nd Edition, p. 106, Motor Design Books LLC, 2010.
Number of Turns per Coil V , rated where
2 f e Nˆ a g , pk 4 .44 f e Nˆ a g , pk
pk
2Bg , pk Dl
P Nˆ a kw Na / 1.1 kw k p kd ks
Na PqNc / C
Na is the number of series turns per phase of armature winding C is the number of parallel circuits of armature winding
Nc
1 . 1V , rated C 2 2 f e qk w B g , pk Dl
Consider leakage flux
Stator Slot Design General Consideration
s ts
bs0
s
ds0ds1
ds
D S
0.4 s ts 0.6 s 3ts d s 7ts Define bs s ts
bs 0 (0.1 ~ 0.5)bs d s 0 (0.1 ~ 0.5)bs
d s1 (0.1 ~ 0.5)bs
Stator Conductor Size Stator current density
J s ,copper
I a ,rated / C Sa
where Sa is stator (armature) conductor cross section area and can be determined from the above formula together with: Air - cooled : 400A/cm 2 J s ,copper 800 A/cm 2
Sa
I a ,rated / C J s ,copper
Permanent Magnets
Samarian Cobalt (SmCo)
Operating temperature of up to 350ºC 2nd strongest rare earth magnet
Neodymium Iron Boron (NdFeB)
Operating temperature of up to 150ºC Strongest rare earth magnet
Permanent Magnet Properties
From Yeadon – Handbook of Small Electric Motors
Rotor Peripheral Speed The maximum allowable peripheral speed of the rotor is a central consideration in machine design. With present-day steel alloys, rotor peripheral speeds of 50,000 ft/min (or about 250 m/s) represent the design limit. 1 ft/min = 0.0051 m/s
Motor Losses (1)
Copper loss
Typical
PCu I 2 R
Stray losses
Electrical phenomenon such as skin and proximity effect
Motor Losses (2)
Core (Iron) Loss
Hysteresis loss Eddy Current loss
PIron h B f n
Mechanical loss
Windage loss Friction loss
c ( Bf ) e ( Bf ) 2
3/ 2
Finite Element Analysis
Fundamental harmonic
J. R. Hendershot and T. J. E. Miller, Design of Brushless Permanent Magnet Machines 2nd Edition, p. 174-175, Motor Design Books LLC, 2010.
Part 2 – Surface Mount Round Rotor Multi-Pole PM Motor Design
Magnetic Circuit Analysis For a multi-pole surface mount rotor
dm Da
D
g
Poles
2 H g g 2 H m d m 0 gBg 0 H m d m 0 dm Bm Am g 0 H m Ag
Bm Am Bg Ag
Working Point for Permanent Magnetics (1) Maximum Energy Point
B
Br BmR
0 Hc
0 HmR
Br B (H H c ) Hc
To get (BH) max
0 H
Br BH (H H c )H Hc
( BH ) Br Hc 0 Bm ,Hm H 2 2
Working Point for Permanent Magnetics (2)
rm
Br 0 H c
1 rm 1.2
Load Line:
Bm
d m Ag 0 H m g Am
Pc 0 H m
Define: Bm m Br
H m (1 m ) H c
Typically pick up: m 0.5 0.9
Pc is called permeance coefficient
Ag / g R m Pg d m Ag Pc g Am Am / d m R g Pm Pc
Bm m rm 0H m 1 m
Airgap Magnetic Field from PM Rotor PM embrace:
B g , rotor
PM PM
Bm
Bm
PM
PM
2
2
B g , rotor B Rh
h 1,3,5...
2
PM
electrical angle
PM 2 2
PM 2
B Rh
2
de
de
P d 2
P Brh cos( h de ) Brh cos( h d ) 2
PM /2 2 PM /2 B h d cos( ) ( Bm ) cos( h ae )d ae m ae ae PM /2 2 PM /2 pitch factor for sin h PM 4 th harmonic 2 B h m h k ph sin h PM 2
Brh
the
Phasor Diagram
V
jX S I A
Bnet
BS
BR EA Typically, design cos 1 at full-load for PMSM. sin 1/3 ( =19.47 ) so that Tfull-load (1 / 3)Tpull out
B g , pk cos B r , pk 0.94 B r , pk Ba , pk sin B r , pk 0.33 B r , pk
Br, pk
PM sin Bm 2 4
Air Gap Size and PM Thickness From: Ba , pk
4 0 Nˆ a 1.5 2 I A,rated gˆ total P
Initial total effective air gap size: gˆ total
From:
gˆ total k c g 'total
4 0 Nˆ a 1.5 2 I A,rated Ba , pk P g 'total g d m / rm
dm Pc g
Pc
Carter’s coefficient g (1 m ) g 'total d m m g 'total rm
( Ag Am )
m rm 1 m
Effective Air Gap gˆ total kc g 'total where the Carter’s coefficient kc
s 2 b s 0 bs 0 g ' total atan ln s 1 2 g ' total bs 0
2 b s 0 2 ' g total
approximately kc
s bs20 s 5 g ' total bs 0
ts
g total
bs0
s
ds0ds1
ds
Rotor Sizing Total rotor diameter, including magnet
Rotor inner diameter
Di Dr 2d m
Dr D 2 g
Part 3 – Two Pole Super High Speed PM Motor with Magnet Inserted in Rotor Shaft
Prototype
Rotor is assembled by heating and cooling. Rotor is welded and well balanced after assembly.
Air Gap Size 2 g eff H g H m D r 0
For a 2-pole PM rotor
( Ag Am )
2 g e ff B m 0 H m D r 0
S
Dr
N
geff
Dr / 2 Bm g e ff 0H
Pc m
Carter’s coefficient g eff
(
g
Dr D 2 2
1 1 D D 1 D k c (1 ) r kc ) r rm 2 rm 2 Pc 2
Dr
Define: Bm m Br
Dr Dr kc ( g ) 2 rm 2 rm
kc
1 1 kc kc Pc rm
H m (1 m ) H c
Typically pick up: m 0.5 0.8
D
g
Pc
D Dr 2
Bm m rm 0H m 1 m
Effective Air Gap gˆ total kc g 'total
gˆ total g eff
Dr , 2 rm
g 'total g
where the Carter’s coefficient s
kc
s
2 bs 0
bs 0 g ' total ln 1 atan 2 ' g b total s0
2 b s 0 2 ' g total
approximately kc
s bs20 s 5 g ' total bs 0
ts
bs0
s g total
ds0ds1
ds
Dr 2 rm
Example - Specifications Design a 2kW, 100krpm, NdFeB-38 PMSM, 2 pole 36 V terminal voltage, Y connected, 90% efficiency.
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